In a device of the above type known from DE-OS 44 17 959, the piston surfaces of the adjusting piston likewise delimit two pressure chambers and the outer surface of the adjusting piston is likewise guided on the inner wall of the housing. To avoid an undesired transfer of the hydraulic pressure medium from one pressure chamber to the other, there is arranged on the outer surface of the adjusting piston, an annular groove in which a steel snap sealing ring is inserted which is slightly biased towards the inner wall of the housing.
A drawback of camshaft adjusting devices of the said type is that by the very presence of the split gap in the steel sealing ring, undesired transfers of the hydraulic pressure medium occur. Moreover, the inner wall of the housing has to be made with a high degree of precision, among other things, to exclude circularity errors which can lead to undesired pressure medium leakages between the pressure chambers. At the same time, due to the steel sealing ring, a high degree of wear is to be expected in the region of sealing and, as a result thereof, a continuously deteriorating sealing effect over the operational life of the device.
Another inherent drawback of camshaft adjusting devices with the aforesaid configuration are their disturbing noises during adjustment which are caused by free float phases and canting of the adjusting piston and sliding sleeve assembly and are transmitted to the housing of the device due to the steel sealing ring on the outer surface of the adjusting piston acting as a bridge for structure-borne noise. It is certainly possible to reduce these noises of adjustment by respecting closer tolerances of flank clearance in the manufacture of the helical gearings of the drive and driven units as well as of the helical gear sections of the sliding sleeve, but this leads to a considerable increase of the manufacturing costs of the device.